2023-03-27 09:58:41

by Igor Artemiev

Subject: [lvc-project] [PATCH] netfilter: nfnetlink: NULL-check skb->dev in __build_packet_message()

After having been compared to NULL value at nfnetlink_log.c:560,
pointer 'skb->dev' is dereferenced at nfnetlink_log.c:576.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Signed-off-by: Igor Artemiev <[email protected]>
---
net/netfilter/nfnetlink_log.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/netfilter/nfnetlink_log.c b/net/netfilter/nfnetlink_log.c
index d97eb280cb2e..2711509eb9a5 100644
--- a/net/netfilter/nfnetlink_log.c
+++ b/net/netfilter/nfnetlink_log.c
@@ -572,7 +572,7 @@ __build_packet_message(struct nfnl_log_net *log,
}
}

- if (indev && skb_mac_header_was_set(skb)) {
+ if (indev && skb->dev && skb_mac_header_was_set(skb)) {
if (nla_put_be16(inst->skb, NFULA_HWTYPE, htons(skb->dev->type)) ||
nla_put_be16(inst->skb, NFULA_HWLEN,
htons(skb->dev->hard_header_len)))
--
2.30.2

2023-03-27 10:25:42

by Pablo Neira Ayuso

Subject: Re: [lvc-project] [PATCH] netfilter: nfnetlink: NULL-check skb->dev in __build_packet_message()

On Mon, Mar 27, 2023 at 12:41:16PM +0300, Igor Artemiev wrote:
> After having been compared to NULL value at nfnetlink_log.c:560,
> pointer 'skb->dev' is dereferenced at nfnetlink_log.c:576.
>
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
>
> Signed-off-by: Igor Artemiev <[email protected]>
> ---
> net/netfilter/nfnetlink_log.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/netfilter/nfnetlink_log.c b/net/netfilter/nfnetlink_log.c
> index d97eb280cb2e..2711509eb9a5 100644
> --- a/net/netfilter/nfnetlink_log.c
> +++ b/net/netfilter/nfnetlink_log.c
> @@ -572,7 +572,7 @@ __build_packet_message(struct nfnl_log_net *log,
> }
> }
>
> - if (indev && skb_mac_header_was_set(skb)) {
> + if (indev && skb->dev && skb_mac_header_was_set(skb)) {

This cannot ever happen, we assume skb->dev is always set on.

> if (nla_put_be16(inst->skb, NFULA_HWTYPE, htons(skb->dev->type)) ||
> nla_put_be16(inst->skb, NFULA_HWLEN,
> htons(skb->dev->hard_header_len)))
> --
> 2.30.2
>

2023-03-27 15:09:01

by Igor Artemiev

Subject: Re: [lvc-project] [PATCH] netfilter: nfnetlink: NULL-check skb->dev in __build_packet_message()

On 3/27/23 13:22, Pablo Neira Ayuso wrote:
> On Mon, Mar 27, 2023 at 12:41:16PM +0300, Igor Artemiev wrote:
>> After having been compared to NULL value at nfnetlink_log.c:560,
>> pointer 'skb->dev' is dereferenced at nfnetlink_log.c:576.
>>
>> Found by Linux Verification Center (linuxtesting.org) with SVACE.
>>
>> Signed-off-by: Igor Artemiev <[email protected]>
>> ---
>> net/netfilter/nfnetlink_log.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/net/netfilter/nfnetlink_log.c b/net/netfilter/nfnetlink_log.c
>> index d97eb280cb2e..2711509eb9a5 100644
>> --- a/net/netfilter/nfnetlink_log.c
>> +++ b/net/netfilter/nfnetlink_log.c
>> @@ -572,7 +572,7 @@ __build_packet_message(struct nfnl_log_net *log,
>> }
>> }
>>
>> - if (indev && skb_mac_header_was_set(skb)) {
>> + if (indev && skb->dev && skb_mac_header_was_set(skb)) {
> This cannot ever happen, we assume skb->dev is always set on.
>
>> if (nla_put_be16(inst->skb, NFULA_HWTYPE, htons(skb->dev->type)) ||
>> nla_put_be16(inst->skb, NFULA_HWLEN,
>> htons(skb->dev->hard_header_len)))
>> --
>> 2.30.2
>>

If skb->dev is always set on, should the check at nfnetlink_log.c:560 be removed?
|

if (indev && skb->dev &&
skb_mac_header_was_set(skb) &&
skb_mac_header_len(skb) != 0) { |

||Thanks, Igor